Optical lens set

ABSTRACT

An optical lens set includes a first lens element of an object-side surface with a convex portion in a vicinity of an optical axis, a second lens element of an image-side surface with a concave portion in a vicinity of its periphery and a sixth lens element of an image-side surface with a convex portion in a vicinity of its periphery. T5min is the minimal distance from the object-side surface of the fifth lens element to the image-side surface of the fifth lens element and the fifth lens element has a fifth lens element thickness T5 along the optical axis to satisfy T5min/T5≤0.6.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of the application Ser. No. 15/272,441, filed on Sep. 22, 2016, which claims priority to Chinese patent application No. 201610804274.5, filed on 2016 Sep. 6, and to Chinese patent application No. 201610635125.0, filed on 2016 Aug. 5. The contents thereof are included herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to an optical imaging lens set. Specifically speaking, the present invention is directed to a shorter optical imaging lens set of six lens elements for use in mobile phones, in cameras, in tablet personal computers, in in-car cameras, or in personal digital assistants (PDA).

2. Description of the Prior Art

In recent years, the popularity of mobile phones and digital cameras makes the sizes of various portable electronic products reduce quickly, and so does those of the photography modules. With the development and shrinkage of a charge coupled device (CCD) or a complementary metal oxide semiconductor element (CMOS), the optical imaging lens set installed in the photography module shrinks as well to meet the demands. The current trend of research is to develop an optical imaging lens set of a shorter length with uncompromised good quality. However, good and necessary optical properties, such as the system aberration improvement, as well as production cost and production feasibility should be taken into consideration, too.

As far as an optical imaging lens set of six lens elements is concerned, the distance between a first object-side surface of the first lens element to an image plane, namely the total length TTL of an optical imaging lens set, is longer to be adversely affect the shrinkage of mobile phones and digital cameras. Accordingly, an optical imaging lens set of good imaging quality, good luminous flux and reduced TTL is still needed.

SUMMARY OF THE INVENTION

In light of the above, the present invention proposes an optical imaging lens set that is smaller, has a low production cost, has an enlarged half of field of view, has a high resolution and has high image quality. The optical imaging lens set of six lens elements of the present invention from an object side toward an image side in order along an optical axis has a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. Each lens element has an object-side surface facing toward an object side as well as an image-side surface facing toward an image side. The optical imaging lens set exclusively has the first lens element, the second lens element, the third lens element, the fourth lens element, the fifth lens element and the sixth lens element with refractive power.

The first lens element has an object-side surface with a convex portion in a vicinity of the optical axis. The second lens element has an image-side surface with a concave portion in a vicinity of its periphery. The sixth lens element has an image-side surface with a convex portion in a vicinity of its periphery.

T₅min is the minimal distance from the object-side surface of the fifth lens element to the image-side surface of the fifth lens element and the fifth lens element has a fifth lens element thickness T₅ along the optical axis to satisfy T₅min/T₅≤0.6.

In the optical imaging lens set of six lens elements of the present invention, ALT is the total thickness of all six lens elements, an air gap G₃₄ between the third lens element and the fourth lens element along the optical axis and an air gap G₅₆ between the fifth lens element and the sixth lens element along the optical axis to satisfy ALT/(G₃₄+G₅₆)≤17.5.

In the optical imaging lens set of six lens elements of the present invention, EFL is the effective focal length of the optical imaging lens set and the third lens element has a third lens element thickness T₃ along the optical axis to satisfy EFL/T₃≤18.5.

In the optical imaging lens set of six lens elements of the present invention, the fourth lens element has a fourth lens element thickness T₄ along the optical axis to satisfy T₅/T₄≤3.5.

In the optical imaging lens set of six lens elements of the present invention, the second lens element has a second lens element thickness T₂ along the optical axis to satisfy ALT/T₂≤13.5.

In the optical imaging lens set of six lens elements of the present invention, the sum of all air gaps AAG between each lens elements from the first lens element to the sixth lens element along the optical axis to satisfy AAG/T₃≥1.8.

In the optical imaging lens set of six lens elements of the present invention, an air gap G₁₂ between the first lens element and the second lens element along the optical axis and an air gap G₂₃ between the second lens element and the third lens element along the optical axis to satisfy EFL/(G₁₂+G₂₃)≤13.

In the optical imaging lens set of six lens elements of the present invention, the first lens element has a first lens element thickness T₁ along the optical axis to satisfy T₁/T₂≤3.6.

In the optical imaging lens set of six lens elements of the present invention, an air gap G₄₅ between the fourth lens element and the fifth lens element along the optical axis to satisfy (G₂₃+G₄₅)/T₂≤4.

The optical imaging lens set of six lens elements of the present invention satisfies T₅/(G₃₄±G₄₅)≤3.5.

In the optical imaging lens set of six lens elements of the present invention, the sixth lens element has a sixth lens element thickness T₅ along the optical axis to satisfy ALT/(T₂+T₆)≤4.4.

The optical imaging lens set of six lens elements of the present invention satisfies EFL/(T₃+T₆)≤6.5.

In the optical imaging lens set of six lens elements of the present invention, the fifth lens element has an image-side surface with a convex portion in a vicinity of the optical axis.

The optical imaging lens set of six lens elements of the present invention satisfies AAG/(T₂+T₃)≤3.5.

The optical imaging lens set of six lens elements of the present invention satisfies T₁/T₃≥1.

The optical imaging lens set of six lens elements of the present invention satisfies (G₂₃+G₅₆)/T₂≤3.6.

The optical imaging lens set of six lens elements of the present invention satisfies EFL/(T₄+T₆)≤5.7.

The optical imaging lens set of six lens elements of the present invention satisfies ALT/(G₂₃+G₃₄)≤8.

The optical imaging lens set of six lens elements of the present invention satisfies EFL/(T₁+T₃)≤5.

The optical imaging lens set of six lens elements of the present invention satisfies T₅/(G₁₂+G₂₃)≤1.8.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrates the methods for determining the surface shapes and for determining one region is a region in a vicinity of the optical axis or the region in a vicinity of its circular periphery of one lens element.

FIG. 6 illustrates a first example of the optical imaging lens set of the present invention.

FIG. 7A illustrates the longitudinal spherical aberration on the image plane of the first example.

FIG. 7B illustrates the astigmatic aberration on the sagittal direction of the first example.

FIG. 7C illustrates the astigmatic aberration on the tangential direction of the first example.

FIG. 7D illustrates the distortion aberration of the first example.

FIG. 8 illustrates a second example of the optical imaging lens set of six lens elements of the present invention.

FIG. 9A illustrates the longitudinal spherical aberration on the image plane of the second example.

FIG. 9B illustrates the astigmatic aberration on the sagittal direction of the second example.

FIG. 9C illustrates the astigmatic aberration on the tangential direction of the second example.

FIG. 9D illustrates the distortion aberration of the second example.

FIG. 10 illustrates a third example of the optical imaging lens set of six lens elements of the present invention.

FIG. 11A illustrates the longitudinal spherical aberration on the image plane of the third example.

FIG. 11B illustrates the astigmatic aberration on the sagittal direction of the third example.

FIG. 11C illustrates the astigmatic aberration on the tangential direction of the third example.

FIG. 11D illustrates the distortion aberration of the third example.

FIG. 12 illustrates a fourth example of the optical imaging lens set of six lens elements of the present invention.

FIG. 13A illustrates the longitudinal spherical aberration on the image plane of the fourth example.

FIG. 13B illustrates the astigmatic aberration on the sagittal direction of the fourth example.

FIG. 13C illustrates the astigmatic aberration on the tangential direction of the fourth example.

FIG. 13D illustrates the distortion aberration of the fourth example.

FIG. 14 illustrates a fifth example of the optical imaging lens set of six lens elements of the present invention.

FIG. 15A illustrates the longitudinal spherical aberration on the image plane of the fifth example.

FIG. 15B illustrates the astigmatic aberration on the sagittal direction of the fifth example.

FIG. 15C illustrates the astigmatic aberration on the tangential direction of the fifth example.

FIG. 15D illustrates the distortion aberration of the fifth example.

FIG. 16 illustrates a sixth example of the optical imaging lens set of six lens elements of the present invention.

FIG. 17A illustrates the longitudinal spherical aberration on the image plane of the sixth example.

FIG. 17B illustrates the astigmatic aberration on the sagittal direction of the sixth example.

FIG. 17C illustrates the astigmatic aberration on the tangential direction of the sixth example.

FIG. 17D illustrates the distortion aberration of the sixth example.

FIG. 18 illustrates a seventh example of the optical imaging lens set of six lens elements of the present invention.

FIG. 19A illustrates the longitudinal spherical aberration on the image plane of the seventh example.

FIG. 19B illustrates the astigmatic aberration on the sagittal direction of the seventh example.

FIG. 19C illustrates the astigmatic aberration on the tangential direction of the seventh example.

FIG. 19D illustrates the distortion aberration of the seventh example.

FIG. 20 illustrates an eighth example of the optical imaging lens set of six lens elements of the present invention.

FIG. 21A illustrates the longitudinal spherical aberration on the image plane of the eighth example.

FIG. 21B illustrates the astigmatic aberration on the sagittal direction of the eighth example.

FIG. 21C illustrates the astigmatic aberration on the tangential direction of the eighth example.

FIG. 21D illustrates the distortion aberration of the eighth example.

FIG. 22 shows the optical data of the first example of the optical imaging lens set.

FIG. 23 shows the aspheric surface data of the first example.

FIG. 24 shows the optical data of the second example of the optical imaging lens set.

FIG. 25 shows the aspheric surface data of the second example.

FIG. 26 shows the optical data of the third example of the optical imaging lens set.

FIG. 27 shows the aspheric surface data of the third example.

FIG. 28 shows the optical data of the fourth example of the optical imaging lens set.

FIG. 29 shows the aspheric surface data of the fourth example.

FIG. 30 shows the optical data of the fifth example of the optical imaging lens set.

FIG. 31 shows the aspheric surface data of the fifth example.

FIG. 32 shows the optical data of the sixth example of the optical imaging lens set.

FIG. 33 shows the aspheric surface data of the sixth example.

FIG. 34 shows the optical data of the seventh example of the optical imaging lens set.

FIG. 35 shows the aspheric surface data of the seventh example.

FIG. 36 shows the optical data of the eighth example of the optical imaging lens set.

FIG. 37 shows the aspheric surface data of the eighth example.

FIG. 38 shows some important ratios in the examples.

DETAILED DESCRIPTION

Before the detailed description of the present invention, the first thing to be noticed is that in the present invention, similar (not necessarily identical) elements are labeled as the same numeral references. In the entire present specification, “a certain lens element has negative/positive refractive power” refers to the part in a vicinity of the optical axis of the lens element has negative/positive refractive power calculated by Gaussian optical theory. An object-side/image-side surface refers to the region which allows imaging light passing through, in the drawing, imaging light includes Lc (chief ray) and Lm (marginal ray). As shown in FIG. 1, the optical axis is “I” and the lens element is symmetrical with respect to the optical axis I. The region A that near the optical axis and for light to pass through is the region in a vicinity of the optical axis, and the region C that the marginal ray passing through is the region in a vicinity of a certain lens element's circular periphery. In addition, the lens element may include an extension part E for the lens element to be installed in an optical imaging lens set (that is the region outside the region C perpendicular to the optical axis). Ideally speaking, no light would pass through the extension part, and the actual structure and shape of the extension part is not limited to this and may have other variations. For the reason of simplicity, the extension part is not illustrated in the following examples. More, precisely, the method for determining the surface shapes or the region in a vicinity of the optical axis, the region in a vicinity of its circular periphery and other regions is described in the following paragraphs:

1. FIG. 1 is a radial cross-sectional view of a lens element. Before determining boundaries of those aforesaid portions, two referential points should be defined first, middle point and conversion point. The middle point of a surface of a lens element is a point of intersection of that surface and the optical axis. The conversion point is a point on a surface of a lens element, where the tangent line of that point is perpendicular to the optical axis. Additionally, if multiple conversion points appear on one single surface, then these conversion points are sequentially named along the radial direction of the surface with numbers starting from the first conversion point. For instance, the first conversion point (closest one to the optical axis), the second conversion point, and the N^(th) conversion point (farthest one to the optical axis within the scope of the clear aperture of the surface). The portion of a surface of the lens element between the middle point and the first conversion point is defined as the portion in a vicinity of the optical axis. The portion located radially outside of the N^(th) conversion point (but still within the scope of the clear aperture) is defined as the portion in a vicinity of a periphery of the lens element. In some embodiments, there are other portions existing between the portion in a vicinity of the optical axis and the portion in a vicinity of a periphery of the lens element; the numbers of portions depend on the numbers of the conversion point(s). In addition, the radius of the clear aperture (or a so-called effective radius) of a surface is defined as the radial distance from the optical axis I to a point of intersection of the marginal ray Lm and the surface of the lens element. 2. Referring to FIG. 2, determining the shape of a portion is convex or concave depends on whether a collimated ray passing through that portion converges or diverges. That is, while applying a collimated ray to a portion to be determined in terms of shape, the collimated ray passing through that portion will be bended and the ray itself or its extension line will eventually meet the optical axis. The shape of that portion can be determined by whether the ray or its extension line meets (intersects) the optical axis (focal point) at the object-side or image-side. For instance, if the ray itself intersects the optical axis at the image side of the lens element after passing through a portion, i.e. the focal point of this ray is at the image side (see point R in FIG. 2), the portion will be determined as having a convex shape. On the contrary, if the ray diverges after passing through a portion, the extension line of the ray intersects the optical axis at the object side of the lens element, i.e. the focal point of the ray is at the object side (see point M in FIG. 2), that portion will be determined as having a concave shape. Therefore, referring to FIG. 2, the portion between the middle point and the first conversion point has a convex shape, the portion located radially outside of the first conversion point has a concave shape, and the first conversion point is the point where the portion having a convex shape changes to the portion having a concave shape, namely the border of two adjacent portions. Alternatively, there is another common way for a person with ordinary skill in the art to tell whether a portion in a vicinity of the optical axis has a convex or concave shape by referring to the sign of an “R” value, which is the (paraxial) radius of curvature of a lens surface. The R value is commonly used in conventional optical design software such as Zemax and CodeV. The R value usually appears in the lens data sheet in the software. For an object-side surface, positive R means that the object-side surface is convex, and negative R means that the object-side surface is concave. Conversely, for an image-side surface, positive R means that the image-side surface is concave, and negative R means that the image-side surface is convex. The result found by using this method should be consistent as by using the other way mentioned above, which determines surface shapes by referring to whether the focal point of a collimated ray is at the object side or the image side. 3. For none conversion point cases, the portion in a vicinity of the optical axis is defined as the portion between 0˜50% of the effective radius (radius of the clear aperture) of the surface, whereas the portion in a vicinity of a periphery of the lens element is defined as the portion between 50˜100% of effective radius (radius of the clear aperture) of the surface.

Referring to the first example depicted in FIG. 3, only one conversion point, namely a first conversion point, appears within the clear aperture of the image-side surface of the lens element. Portion I is a portion in a vicinity of the optical axis, and portion II is a portion in a vicinity of a periphery of the lens element. The portion in a vicinity of the optical axis is determined as having a concave surface due to the R value at the image-side surface of the lens element is positive. The shape of the portion in a vicinity of a periphery of the lens element is different from that of the radially inner adjacent portion, i.e. the shape of the portion in a vicinity of a periphery of the lens element is different from the shape of the portion in a vicinity of the optical axis; the portion in a vicinity of a periphery of the lens element has a convex shape.

Referring to the second example depicted in FIG. 4, a first conversion point and a second conversion point exist on the object-side surface (within the clear aperture) of a lens element. In which portion I is the portion in a vicinity of the optical axis, and portion III is the portion in a vicinity of a periphery of the lens element. The portion in a vicinity of the optical axis has a convex shape because the R value at the object-side surface of the lens element is positive. The portion in a vicinity of a periphery of the lens element (portion III) has a convex shape. What is more, there is another portion having a concave shape existing between the first and second conversion point (portion II).

Referring to a third example depicted in FIG. 5, no conversion point exists on the object-side surface of the lens element. In this case, the portion between 0˜50% of the effective radius (radius of the clear aperture) is determined as the portion in a vicinity of the optical axis, and the portion between 50˜100% of the effective radius is determined as the portion in a vicinity of a periphery of the lens element. The portion in a vicinity of the optical axis of the object-side surface of the lens element is determined as having a convex shape due to its positive R value, and the portion in a vicinity of a periphery of the lens element is determined as having a convex shape as well.

As shown in FIG. 6, the optical imaging lens set 1 of six lens elements of the present invention, sequentially located from an object side 2 (where an object is located) to an image side 3 along an optical axis 4, has an aperture stop (ape. stop) 80, a first lens element 10, a second lens element 20, a third lens element 30, a fourth lens element 40, a fifth lens element 50, a sixth lens element 60, a filter 70 and an image plane 71. Generally speaking, the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the sixth lens element 60 may be made of a transparent plastic material but the present invention is not limited to this, and each has an appropriate refractive power. There are exclusively six lens elements, which means the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the sixth lens element 60, with refractive power in the optical imaging lens set 1 of the present invention. The optical axis 4 is the optical axis of the entire optical imaging lens set 1, and the optical axis of each of the lens elements coincides with the optical axis of the optical imaging lens set 1.

Furthermore, the optical imaging lens set 1 includes an aperture stop (ape. stop) 80 disposed in an appropriate position. In FIG. 6, the aperture stop 80 is disposed between the object side 2 and the first lens element 10. When light emitted or reflected by an object (not shown) which is located at the object side 2 enters the optical imaging lens set 1 of the present invention, it forms a clear and sharp image on the image plane 71 at the image side 3 after passing through the aperture stop 80, the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50, the sixth lens element 60 and the filter 70. In one embodiments of the present invention, the optional filter 70 may be a filter of various suitable functions, for example, the filter 70 may be an infrared cut filter (IR cut filter), placed between the image-side surface 62 of the sixth lens element 60 and the image plane 71.

Each lens element in the optical imaging lens set 1 of the present invention has an object-side surface facing toward the object side 2 as well as an image-side surface facing toward the image side 3. For example, the first lens element 10 has a first object-side surface 11 and a first image-side surface 12; the second lens element 20 has a second object-side surface 21 and a second image-side surface 22; the third lens element 30 has a third object-side surface 31 and a third image-side surface 32; the fourth lens element 40 has a fourth object-side surface 41 and a fourth image-side surface 42; the fifth lens element 50 has a fifth object-side surface 51 and a fifth image-side surface 52; the sixth lens element 60 has a sixth object-side surface 61 and a sixth image-side surface 62. In addition, each object-side surface and image-side surface in the optical imaging lens set 1 of the present invention has a part (or portion) in a vicinity of its circular periphery (circular periphery part) away from the optical axis 4 as well as a part in a vicinity of the optical axis (optical axis part) close to the optical axis 4.

Each lens element in the optical imaging lens set 1 of the present invention further has a central thickness T on the optical axis 4. For example, the first lens element 10 has a first lens element thickness T₁, the second lens element 20 has a second lens element thickness T₂, the third lens element 30 has a third lens element thickness T₃, the fourth lens element 40 has a fourth lens element thickness T₄, the fifth lens element 50 has a fifth lens element thickness T₅, the sixth lens element 60 has a sixth lens element thickness T₅. Therefore, the total thickness of all the lens elements in the optical imaging lens set 1 along the optical axis 4 is ALT=T₁+T₂+T₃+T₄+T₅+T₆.

The present invention in particular indicates that the fifth lens element 50 has a minimal lens thickness T₅min. T₅min is the minimal distance from a percent point, namely an object-side percent point, on the object-side surface 51 of the fifth lens element 50 to another percent point, namely an image-side percent point, on the image-side surface 52 of the fifth lens element 50. The effective radii of both the object-side surface 51 of the fifth lens element 50 and the image-side surface 52 of the fifth lens element 50 are equally divided into 100 percent points. Each percent point on each surface is respectively called an O^(th) object-side percent point and an I^(th) image-side percent point so there are 100 object-side percent points on the object-side surface 51 in total and 100 image-side percent points on the image-side surface 52 in total. The coordinate (O^(th), I^(th)) is used to denote T₅min.

For example, the first object-side percent point is the 0th percent point (the coordinate) at the optical axis 4, the 51^(th) object-side percent point is (50) at the midpoint and the last object-side percent point is (100) at its periphery. Similarly, the first image-side percent point is the 0^(th) percent point (the coordinate) at the optical axis 4, the 51^(th) image-side percent point is (50) at the midpoint and the last image-side percent point is (100) at its periphery.

In addition, between two adjacent lens elements in the optical imaging lens set 1 of the present invention there is an air gap along the optical axis 4. For example, an air gap G₁₂ is disposed between the first lens element 10 and the second lens element 20, an air gap G₂₃ is disposed between the second lens element 20 and the third lens element 30, an air gap G₃₄ is disposed between the third lens element 30 and the fourth lens element 40, an air gap G₄₅ is disposed between the fourth lens element 40 and the fifth lens element 50 as well as an air gap G₅₆ is disposed between the fifth lens element 50 and the sixth lens element 60. Therefore, the sum of total five air gaps between adjacent lens elements from the first lens element 10 to the sixth lens element 60 along the optical axis 4 is AAG=G₁₂+G₂₃+G₃₄+G₄₅+G₅₆.

In addition, the distance between the first object-side surface 11 of the first lens element 10 to the image plane 71, namely the total length of the optical imaging lens set along the optical axis 4 is TTL; the effective focal length of the optical imaging lens set is EFL; the distance between the sixth image-side surface 62 of the sixth lens element 60 to the image plane 71 along the optical axis 4 is BFL.

Furthermore, the focal length of the first lens element 10 is f1; the focal length of the second lens element 20 is f2; the focal length of the third lens element 30 is f3; the focal length of the fourth lens element 40 is f4; the focal length of the fifth lens element 50 is f5; the focal length of the sixth lens element 60 is f6; the refractive index of the first lens element 10 is n1; the refractive index of the second lens element 20 is n2; the refractive index of the third lens element 30 is n3; the refractive index of the fourth lens element 40 is n4; the refractive index of the fifth lens element 50 is n5; the refractive index of the sixth lens element 60 is n6; the Abbe number of the first lens element 10 is ν1; the Abbe number of the second lens element 20 is ν2; the Abbe number of the third lens element 30 is ν3; and the Abbe number of the fourth lens element 40 is ν4; the Abbe number of the fifth lens element 50 is ν5; and the Abbe number of the sixth lens element 60 is ν6.

First Example

Please refer to FIG. 6 which illustrates the first example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 7A for the longitudinal spherical aberration on the image plane 71 of the first example; please refer to FIG. 7B for the astigmatic field aberration on the sagittal direction; please refer to FIG. 7C for the astigmatic field aberration on the tangential direction, and please refer to FIG. 7D for the distortion aberration. The Y axis of the spherical aberration in each example is “field of view” for 1.0. The Y axis of the astigmatic field and the distortion in each example stands for “image height”, which is 3.5 mm.

The optical imaging lens set 1 of the first example has six lens elements 10 to 60 with refractive power. The optical imaging lens set 1 also has a filter 70, an aperture stop 80, and an image plane 71. The aperture stop 80 is provided between the object side 2 and the first lens element 10. The filter 70 may be used for preventing specific wavelength light (such as the infrared light) reaching the image plane to adversely affect the imaging quality.

The first lens element 10 has positive refractive power. The first object-side surface 11 facing toward the object side 2 has a convex part 13 in the vicinity of the optical axis and a convex part 14 in a vicinity of its circular periphery. The first image-side surface 12 facing toward the image side 3 has a concave part 16 in the vicinity of the optical axis and a convex part 17 in a vicinity of its circular periphery. Besides, both the first object-side surface 11 and the first image-side 12 of the first lens element 10 are aspherical surfaces.

The second lens element 20 has negative refractive power. The second object-side surface 21 facing toward the object side 2 has a convex part 23 in the vicinity of the optical axis and a convex part 24 in a vicinity of its circular periphery. The second image-side surface 22 facing toward the image side 3 has a concave part 26 in the vicinity of the optical axis and a concave part 27 in a vicinity of its circular periphery. Both the second object-side surface 21 and the second image-side 22 of the second lens element 20 are aspherical surfaces.

The third lens element 30 has negative refractive power. The third object-side surface 31 facing toward the object side 2 has a convex part 33 in the vicinity of the optical axis and a concave part 34 in a vicinity of its circular periphery. The third image-side surface 32 facing toward the image side 3 has a concave part 36 in the vicinity of the optical axis and a convex part 37 in a vicinity of its circular periphery. Both the third object-side surface 31 and the third image-side 32 of the third lens element 30 are aspherical surfaces.

The fourth lens element 40 has negative refractive power. The fourth object-side surface 41 facing toward the object side 2 has a convex part 43 in the vicinity of the optical axis and a concave part 44 in a vicinity of its circular periphery. The fourth image-side surface 42 facing toward the image side 3 has a concave part 46 in the vicinity of the optical axis and a convex part 47 in a vicinity of its circular periphery. Both the fourth object-side surface 41 and the fourth image-side 42 of the fourth lens element 40 are aspherical surfaces.

The fifth lens element 50 has positive refractive power. The fifth object-side surface 51 facing toward the object side 2 has a concave part 53 in the vicinity of the optical axis and a concave part 54 in a vicinity of its circular periphery. The fifth image-side surface 52 facing toward the image side 3 has a convex part 56 in the vicinity of the optical axis and a convex part 57 in a vicinity of its circular periphery. Both the fifth object-side surface 51 and the fifth image-side 52 of the fifth lens element 50 are aspherical surfaces.

The sixth lens element 60 has negative refractive power. The sixth object-side surface 61 facing toward the object side 2 has a concave part 63 in the vicinity of the optical axis and a convex part 64 in a vicinity of its circular periphery. The sixth image-side surface 62 facing toward the image side 3 has a concave part 66 in the vicinity of the optical axis and a convex part 67 in a vicinity of its circular periphery. Both the sixth object-side surface 61 and the sixth image-side 62 of the sixth lens element 60 are aspherical surfaces. The filter 70 is disposed between the sixth image-side 62 of the sixth lens element 60 and the image plane 71.

In the first lens element 10, the second lens element 20, the third lens element 30, the fourth lens element 40, the fifth lens element 50 and the sixth lens element 60 of the optical imaging lens element 1 of the present invention, there are 12 surfaces, such as the object-side surfaces 11/21/31/41/51/61 and the image-side surfaces 12/22/32/42/52/62. If a surface is aspherical, these aspheric coefficients are defined according to the following formula:

${Z(Y)} = {{\frac{Y^{2}}{R}/\left( {1 + \sqrt{1 - {\left( {1 + K} \right)\frac{Y^{2}}{R^{2}}}}} \right)} + {\sum\limits_{i = 1}^{n}{a_{2i} \times Y^{2i}}}}$

In which: R represents the curvature radius of the lens element surface; Z represents the depth of an aspherical surface (the perpendicular distance between the point of the aspherical surface at a distance Y from the optical axis and the tangent plane of the vertex on the optical axis of the aspherical surface); Y represents a vertical distance from a point on the aspherical surface to the optical axis; K is a conic constant; a_(2i) is the aspheric coefficient of the 2i^(th) order.

The optical data of the first example of the optical imaging lens set 1 are shown in FIG. 22 while the aspheric surface data are shown in FIG. 23. In the present examples of the optical imaging lens set, the f-number of the entire optical lens element system is Fno, EFL is the effective focal length, HFOV stands for the half field of view which is half of the field of view of the entire optical lens element system, and the unit for the curvature radius, the thickness and the focal length is in millimeters (mm). TTL is 6.010 mm. Fno is 1.79. The image height is 3.5 mm. HFOV is 35.913 degrees. T₅min (95, 88) is 0.412 mm.

Second Example

Please refer to FIG. 8 which illustrates the second example of the optical imaging lens set 1 of the present invention. It is noted that from the second example to the following examples, in order to simplify the figures, only the components different from what the first example has, and the basic lens elements will be labeled in figures. Other components that are the same as what the first example has, such as the object-side surface, the image-side surface, the part in a vicinity of the optical axis and the part in a vicinity of its circular periphery will be omitted in the following examples. Please refer to FIG. 9A for the longitudinal spherical aberration on the image plane 71 of the second example, please refer to FIG. 9B for the astigmatic aberration on the sagittal direction, please refer to FIG. 9C for the astigmatic aberration on the tangential direction, and please refer to FIG. 9D for the distortion aberration. The components in the second example are similar to those in the first example, but the optical data such as the curvature radius, the refractive power, the lens thickness, the lens focal length, the aspheric surface or the back focal length in this example are different from the optical data in the first example, and in this example, the sixth object-side surface 61 has a concave 64 part in a vicinity of its circular periphery. The optical data of the second example of the optical imaging lens set are shown in FIG. 24 while the aspheric surface data are shown in FIG. 25. TTL is 5.944 mm. Fno is 1.78. The image height is 3.5 mm. HFOV is 36.134 degrees. T₅min (83, 79) is 0.443 mm. In particular, 1) the TTL of the second example is shorter than that of the first example of the present invention, 2) the HFOV of the second example is better than that of the first example of the present invention, and 3) the Fno of the second example is better than that of the first example of the present invention.

Third Example

Please refer to FIG. 10 which illustrates the third example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 11A for the longitudinal spherical aberration on the image plane 71 of the third example; please refer to FIG. 11B for the astigmatic aberration on the sagittal direction; please refer to FIG. 11C for the astigmatic aberration on the tangential direction, and please refer to FIG. 11D for the distortion aberration. The components in the third example are similar to those in the first example, but the optical data such as the curvature radius, the refractive power, the lens thickness, the lens focal length, the aspheric surface or the back focal length in this example are different from the optical data in the first example, and in this example, the sixth object-side surface 61 has a concave 64 part in a vicinity of its circular periphery.

The optical data of the third example of the optical imaging lens set are shown in FIG. 26 while the aspheric surface data are shown in FIG. 27. TTL is 5.965 mm. Fno is 1.78. The image height is 3.5 mm. HFOV is 36.147 degrees. T₅min (84, 80) is 0.430 mm. In particular, 1) the TTL of the third example is shorter than that of the first example of the present invention, 2) the HFOV of the third example is better than that of the first example of the present invention, and 3) the Fno of the third example is better than that of the first example of the present invention so the yield would be better.

Fourth Example

Please refer to FIG. 12 which illustrates the fourth example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 13A for the longitudinal spherical aberration on the image plane 71 of the fourth example; please refer to FIG. 13B for the astigmatic aberration on the sagittal direction; please refer to FIG. 13C for the astigmatic aberration on the tangential direction, and please refer to FIG. 13D for the distortion aberration. The components in the fourth example are similar to those in the first example, but the optical data such as the curvature radius, the refractive power, the lens thickness, the lens focal length, the aspheric surface or the back focal length in this example are different from the optical data in the first example.

The optical data of the fourth example of the optical imaging lens set are shown in FIG. 28 while the aspheric surface data are shown in FIG. 29. TTL is 5.955 mm. Fno is 1.80. The image height is 3.5 mm. HFOV is 35.807 degrees. T₅min (92, 86) is 0.327 mm. In particular, the TTL of the fourth example is shorter than that of the first example of the present invention.

Fifth Example

Please refer to FIG. 14 which illustrates the fifth example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 15A for the longitudinal spherical aberration on the image plane 71 of the fifth example; please refer to FIG. 15B for the astigmatic aberration on the sagittal direction; please refer to FIG. 15C for the astigmatic aberration on the tangential direction, and please refer to FIG. 15D for the distortion aberration. The components in the fifth example are similar to those in the first example, but the optical data such as the curvature radius, the refractive power, the lens thickness, the lens focal length, the aspheric surface or the back focal length in this example are different from the optical data in the first example.

The optical data of the fifth example of the optical imaging lens set are shown in FIG. 30 while the aspheric surface data are shown in FIG. 31. TTL is 5.871 mm. Fno is 1.74. The image height is 3.5 mm. HFOV is 36.753 degrees. T₅min (86, 83) is 0.313 mm. In particular, 1) the TTL of the fifth example is shorter than that of the first example of the present invention, 2) the HFOV of the fifth example is better than that of the first example of the present invention, and 3) the Fno of the fifth example is better than that of the first example of the present invention and the yield would be better.

Sixth Example

Please refer to FIG. 16 which illustrates the sixth example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 17A for the longitudinal spherical aberration on the image plane 71 of the sixth example; please refer to FIG. 17B for the astigmatic aberration on the sagittal direction; please refer to FIG. 17C for the astigmatic aberration on the tangential direction, and please refer to FIG. 17D for the distortion aberration. The components in the sixth example are similar to those in the first example, but the optical data such as the curvature radius, the refractive power, the lens thickness, the lens focal length, the aspheric surface or the back focal length in this example are different from the optical data in the first example.

The optical data of the sixth example of the optical imaging lens set are shown in FIG. 32 while the aspheric surface data are shown in FIG. 33. TTL is 5.896 mm. Fno is 1.73. The image height is 3.5 mm. HFOV is 37.047 degrees. T₅min (98, 89) is 0.464 mm. In particular, 1) the TTL of the sixth example is shorter than that of the first example of the present invention, 2) the HFOV of the sixth example is better than that of the first example of the present invention, and 3) the Fno of the sixth example is better than that of the first example of the present invention and the yield would be better.

Seventh Example

Please refer to FIG. 18 which illustrates the seventh example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 19A for the longitudinal spherical aberration on the image plane 71 of the seventh example; please refer to FIG. 19B for the astigmatic aberration on the sagittal direction; please refer to FIG. 19C for the astigmatic aberration on the tangential direction, and please refer to FIG. 19D for the distortion aberration. The components in the seventh example are similar to those in the first example, but the optical data such as the curvature radius, the refractive power, the lens thickness, the lens focal length, the aspheric surface or the back focal length in this example are different from the optical data in the first example.

The optical data of the seventh example of the optical imaging lens set are shown in FIG. 34 while the aspheric surface data are shown in FIG. 35. TTL is 5.862 mm. Fno is 1.76. The image height is 3.5 mm. HFOV is 36.447 degrees. T₅min (77, 73) is 0.282 mm. In particular, 1) the TTL of the seventh example is shorter than that of the first example of the present invention, 2) the HFOV of the seventh example is better than that of the first example of the present invention, and 3) the Fno of the seventh example is better than that of the first example of the present invention.

Eighth Example

Please refer to FIG. 20 which illustrates the eighth example of the optical imaging lens set 1 of the present invention. Please refer to FIG. 21A for the longitudinal spherical aberration on the image plane 71 of the eighth example; please refer to FIG. 21B for the astigmatic aberration on the sagittal direction; please refer to FIG. 21C for the astigmatic aberration on the tangential direction, and please refer to FIG. 21D for the distortion aberration. The components in the eighth example are similar to those in the first example, but the optical data such as the curvature radius, the refractive power, the lens thickness, the lens focal length, the aspheric surface or the back focal length in this example are different from the optical data in the first example.

The optical data of the eighth example of the optical imaging lens set are shown in FIG. 36 while the aspheric surface data are shown in FIG. 37. TTL is 5.911 mm. Fno is 1.73. The image height is 3.5 mm. HFOV is 37.088 degrees. T₅min (95, 87) is 0.397 mm. In particular, 1) the TTL of the eighth example is shorter than that of the first example of the present invention, 2) the HFOV of the eighth example is better than that of the first example of the present invention, and 3) the Fno of the eighth example is better than that of the first example of the present invention.

Some important ratios in each example are shown in FIG. 38. The distance between the sixth image-side surface 62 of the sixth lens element 60 to the filter 70 along the optical axis 4 is G6F; the thickness of the filter 70 along the optical axis 4 is TF; the distance between the filter 70 to the image plane 71 along the optical axis 4 is GFP; the distance between the sixth image-side surface 62 of the sixth lens element 60 to the image plane 71 along the optical axis 4 is BFL. Therefore, BFL=G6F+TF+GFP.

In the light of the above examples, the inventors observe at least the following features:

1. The first object-side surface of the first lens element with a convex portion in a vicinity of the optical axis helps concentrate the light effectively. 2. The second lens element has an image-side surface with a concave portion in a vicinity of its periphery. The sixth lens element has an image-side surface with a convex portion in a vicinity of its periphery. The above arrangements collectively reduce the aberration of the optical imaging lens set, and eliminate the curvature of field and the distortion to maintain a good imaging quality. In addition, the above curvatures to go with the limitation of T₅min/T₅≤0.6 effectively improve the imaging quality. Preferably, the image-side surface of the fifth lens element with a convex portion in a vicinity of the optical axis helps the correction of the aberration.

In addition, the inventors discover that there are some better ratio ranges for different data according to the above various important ratios. Better ratio ranges help the designers to design a better optical performance and an effectively reduce length of a practically possible optical imaging lens set. For example:

1. ALT/(G₃₄+G₅₆)≤17.5. Preferably, the ratio may be 3.7˜17.5. 2. EFL/T₃≤18.5. Preferably, the ratio may be 6.7˜18.5. 3. T₅/T₄≤3.5. Preferably, the ratio may be 1.0˜3.5. 4. ALT/T₂≤13.5. Preferably, the ratio may be 9.5˜13.5. 5. AAG/T₃≥1.8. Preferably, the ratio may be 1.8˜6.3. 6. EFL/(G₁₂+G₂₃)≤13.0. Preferably, the ratio may be 6.5˜13.0. 7. T₁/T₂≤3.6. Preferably, the ratio may be 2.3˜3.6. 8. (G₂₃+G₄₅)/T₂≤4.0. Preferably, the ratio may be 2.0˜4.0. 9. T₅/(G₃₄+G₄₅)≤3.5. Preferably, the ratio may be 0.6˜3.5. 10. ALT/(T₂+T₆)≤4.4. Preferably, the ratio may be 3.2˜4.4. 11. EFL/(T₃+T₆)≤6.5. Preferably, the ratio may be 3.6˜6.5. 12. AAG/(T₂+T₃)≤3.5. Preferably, the ratio may be 1.2˜3.5. 13. T₁/T₃≥1.0. Preferably, the ratio may be 1.0˜3.1. 14. (G₂₃+G₅₆)/T₂≤3.6. Preferably, the ratio may be 2.0˜3.6. 15. EFL/(T₄+T₆)≤5.7. Preferably, the ratio may be 4.3˜5.7. 16. ALT/(G₂₃+G₃₄)≤8.0. Preferably, the ratio may be 4.3˜8.0. 17. EFL/(T₁+T₃)≤5.0. Preferably, the ratio may be 3.2˜5.0. 18. T₅/(G₁₂+G₂₃)≤1.8. Preferably, the ratio may be 1.1˜1.8.

The above adjustments take the easiness of the fabrication into consideration so at the same time they have the benefits of high yield.

In the light of the unpredictability of the optical imaging lens set, the present invention suggests the above principles. The above limitations may be properly combined at the discretion of persons who practice the present invention and they are not limited as shown above.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. An optical imaging lens set, from an object side toward an image side in order along an optical axis comprising: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element, said first lens element to said sixth lens element each having an object-side surface facing toward the object side as well as an image-side surface facing toward the image side, wherein: said first lens element has an image-side surface with a concave portion in a vicinity of said optical axis; and said fourth lens element has an object-side surface with a convex portion in a vicinity of said optical axis, said optical imaging lens set exclusively has six lens elements with refractive power, said first lens element has a first lens element thickness T₁ along said optical axis, said fourth lens element has a fourth lens element thickness T₄ along said optical axis, said fifth lens element has a fifth lens element thickness T₅ along said optical axis and an air gap G₄₅ between said fourth lens element and said fifth lens element along said optical axis to satisfy 1.475≤(T₄+G₄₅+T₅)/T₁≤1.751.
 2. The optical imaging lens as claimed in claim 1, satisfying EFL/(G₁₂+G₂₃)≤13, where EFL is an effective focal length of the optical imaging lens set, an air gap G₁₂ is between said first lens element and said second lens element along said optical axis and an air gap G₂₃ is between said second lens element and said third lens element along said optical axis.
 3. The optical imaging lens as claimed in claim 1, satisfying T₅/(G₁₂+G₂₃)≤1.8, where an air gap G₁₂ is between said first lens element and said second lens element along said optical axis and an air gap G₂₃ is between said second lens element and said third lens element along said optical axis.
 4. The optical imaging lens as claimed in claim 1, satisfying 4.132≤(T₄+G₄₅+T₅+G₅₆)/T₂≤6.641, where said second lens element has a second lens element thickness T₂ along said optical axis and an air gap G₅₆ is between said fifth lens element and said sixth lens element along said optical axis.
 5. The optical imaging lens as claimed in claim 1, satisfying 1.756≤(T₂+T₄+G₄₅+T₅)/T₁≤2.086, where said second lens element has a second lens element thickness T₂ along said optical axis.
 6. The optical imaging lens as claimed in claim 1, satisfying 1.394≤(G₁₂+T₄+T₅)/(T₃+G₅₆)≤2.164, where said third lens element has a third lens element thickness T₃ along said optical axis, an air gap G₁₂ is between said first lens element and said second lens element along said optical axis and an air gap G₅₆ is between said fifth lens element and said sixth lens element along said optical axis.
 7. The optical imaging lens as claimed in claim 1, satisfying 1.557≤(G₁₂+T₄+G₄₅+T₅)/(T₃+G₅₆)≤2.475, where said third lens element has a third lens element thickness T₃ along said optical axis, an air gap G₁₂ is between said first lens element and said second lens element along said optical axis and an air gap G₅₆ is between said fifth lens element and said sixth lens element along said optical axis.
 8. An optical imaging lens set, from an object side toward an image side in order along an optical axis comprising: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element, said first lens element to said sixth lens element each having an object-side surface facing toward the object side as well as an image-side surface facing toward the image side, wherein: said first lens element has an image-side surface with a concave portion in a vicinity of the optical axis; said second lens element an object-side surface with a convex portion in a vicinity of the optical axis; and said fourth lens element has an object-side surface with a convex portion in a vicinity of the optical axis, the optical imaging lens set exclusively has six lens elements with refractive power, said second lens element has a second lens element thickness T₂ along said optical axis, said third lens element has a third lens element thickness T₃ along said optical axis, said fourth lens element has a fourth lens element thickness T₄ along said optical axis, said fifth lens element has a fifth lens element thickness T₅ along the optical axis, an air gap G₃₄ is between said third lens element and said fourth lens element along said optical axis, an air gap G₄₅ is between said fourth lens element and said fifth lens element along said optical axis and an air gap G₅₆ is between said fifth lens element and said sixth lens element along said optical axis to satisfy 1.987≤(G₃₄+T₄+G₄₅+T₅+G₅₆)/(T₂+T₃)≤2.598.
 9. The optical imaging lens as claimed in claim 8, satisfying ALT/(G₃₄+G₅₆)≤17.5, where ALT is a total thickness of all six lens elements.
 10. The optical imaging lens as claimed in claim 8, satisfying ALT/T₂≤13.5, where ALT is a total thickness of all six lens elements.
 11. The optical imaging lens as claimed in claim 8, satisfying AAG/T₃≥1.8, where a sum of all air gaps AAG is between each lens elements from said first lens element to said sixth lens element along said optical axis.
 12. The optical imaging lens as claimed in claim 8, satisfying (G₂₃+G₄₅)/T₂≤4, where an air gap G₂₃ is between said second lens element and said third lens element along said optical axis.
 13. The optical imaging lens as claimed in claim 8, satisfying T₁/T₃≥1, where said first lens element has a first lens element thickness T₁ along said optical axis.
 14. The optical imaging lens as claimed in claim 8, satisfying ALT/(G₂₃+G₃₄)≤8, where ALT is a total thickness of all six lens elements and an air gap G₂₃ is between said second lens element and said third lens element along said optical axis.
 15. An optical imaging lens set, from an object side toward an image side in order along an optical axis comprising: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element, said first lens element to said sixth lens element each having an object-side surface facing toward the object side as well as an image-side surface facing toward the image side, wherein: said first lens element has an image-side surface with a concave portion in a vicinity of the optical axis; said second lens element an object-side surface with a convex portion in a vicinity of the optical axis; and said fourth lens element has an object-side surface with a convex portion in a vicinity of the optical axis, the optical imaging lens set exclusively has six lens elements with refractive power, said second lens element has a second lens element thickness T₂ along said optical axis and an air gap G₄₅ is between said fourth lens element and said fifth lens element along said optical axis to satisfy T₂>G₄₅.
 16. The optical imaging lens as claimed in claim 15, satisfying (G₂₃+G₅₆)/T₂≤3 0.6, where an air gap G₂₃ is between said second lens element and said third lens element along said optical axis and an air gap G₅₆ is between said fifth lens element and said sixth lens element along said optical axis.
 17. The optical imaging lens as claimed in claim 15, satisfying EFL/(T₄+T₆)≤5.7, where EFL is an effective focal length of the optical imaging lens set, said fourth lens element has a fourth lens element thickness T₄ along said optical axis and said sixth lens element has a sixth lens element thickness T₆ along said optical axis.
 18. The optical imaging lens as claimed in claim 15, satisfying 1.748≤(G₃₄+T₄+G₄₅+T₅)/(T₂+T₃)≤2.318, where said third lens element has a third lens element thickness T₃ along said optical axis, said fourth lens element has a fourth lens element thickness T₄ along said optical axis, said fifth lens element has a fifth lens element thickness T₅ along the optical axis, and an air gap G₃₄ is between said third lens element and said fourth lens element along said optical axis.
 19. The optical imaging lens as claimed in claim 15, satisfying 0.717≤(G₁₂+G₃₄+T₄+G₄₅)/(T₃+G₅₆)≤1.210, where said third lens element has a third lens element thickness T₃ along said optical axis, said fourth lens element has a fourth lens element thickness T₄ along said optical axis, an air gap G₁₂ is between said first lens element and said second lens element along said optical axis, an air gap G₃₄ is between said third lens element and said fourth lens element along said optical axis and an air gap G₅₆ is between said fifth lens element and said sixth lens element along said optical axis.
 20. The optical imaging lens as claimed in claim 15, satisfying 6.474≤TTL/T1≤7.191, where TTL is a distance between a first object-side surface of said first lens element and an image plane, and said first lens element has a first lens element thickness T₁ along said optical axis. 